Estimation in step-stress accelerated life tests for the exponentiated exponential distribution with type-I censoring

The step-stress accelerated life tests allow the experimenter to increase the stress levels at fixed times during the experiment. The lifetime of a product at any level of stress is assumed to have an exponentiated distribution, whose baseline distribution is a general class of distributions which includes, among others, Weibull, compound Weibull, Pareto, Gompertz, normal and logistic distributions. The scale parameter of the baseline distribution is assumed to be a log-linear function of the stress and a cumulative exposure model holds. Special attention is paid to an exponentiated exponential distribution. Based on type-I censoring, the maximum likelihood estimates of the parameters under consideration are obtained. A Monte Carlo simulation study is carried out to investigate the precision of the maximum likelihood estimates and to obtain the coverage probabilities of the bootstrap confidence intervals for the parameters involved. Finally, an example is presented to illustrate the two discussed methods of bootstrap confidence intervals.     

A prediction system for assessing customer affordability of whole life cycle cost in defence industry

The manufacturing, delivery and support of service contracts in defence aerospace industry require a high financial investment. It is essential that the customer has the financial ability to procure and support the contract from the conceptual and manufacturing phase to the end of the project given the budget constraints. The aim of this paper is to identify the factors that affect customer affordability of defence contracts and develop a customer affordability assessment framework which is implemented as a software prototype system. Two major quantitative factors and twelve qualitative factors were identified, out which seven factors (identified as the major factors) were included within the customer affordability system. Following the identification of factors and development of measures for each, suggested actions to improve customer affordability were also proposed. The research methodology combined both case study and literature review approach with industrial collaboration in the customer affordability system development. The customer affordability system was validated through collaboration with industrial partners and a case study from defence sector and the results showed that the customer affordability system was capable of providing a good assessment of customer affordability.     

Database accuracy: Results from a survey of database vendors

The accuracy of databases is the subject of our survey of vendors of databases. This study examines external databases. Among the issues covered by the survey are: selection criteria for data sources, formats of data, and the approaches followed in maintaining database accuracy. One specific focus of the study is external databases for forecasting. Forecasting, as a tool of managerial planning, is sensitive to the availability and accuracy of databases. The survey results suggest that there are some practices followed by database suppliers that could produce unreliable information.     

紫外可见光谱区分光光度计的标准化

紫外可见光谱测量通常用于实验室的定性和定量分析。为确保测量值可靠,实验仪器必须经过校准。埃及国家标准化所建立了一种光度测定法,其吸收和传输能力满足国际和国家要求。本文介绍了紫外可见光谱测及测量仪,讨论了影响测量可靠性的因素,并讨论了包含相关测量参数的不确定度模型。     

Die zeitliche Entwicklung positiver Entladungskanäle längs der Oberfläche von Isolierfilmen

Ohne ZusammenfassungMit 7 Textabbildungen     

Quality and safety of irradiated food regarding biogenic amines: Ras cheese

Food safety and quality became very important, especially with the challenge to ensure safe and healthy foods in regard to chemical hazards. So, this study was conducted to evaluate the quality and safety of irradiated Ras cheese during the storage period, with respect to biogenic amines (BAs). Ras cheese was manufactured, ripened and irradiated by γ‐irradiation at 0, 5, 10 and 15 kGy. The samples were stored in refrigerator at 5 ± 1 °C from where samples were withdrawn at 0, 2, 4 and 6 months for analysis. The results revealed that most sensory scores and chemical properties showed insignificant differences (P ≤ 0.05). The microbial counts were reduced with different degrees according to both storage period and irradiation dose. Also, irradiation was effective in reducing the content of BAs without harming the chemical properties of Ras cheese. The total content of BAs reflects the safety of irradiated Ras cheese and also indicates a high‐quality product in comparison with nonirradiated samples.     

Cancelable fusion-based face recognition

Multimedia Tools and Applications - Biometric recognition refers to the automated process of recognizing individuals using their biometric patterns. Recent advancements in deep learning and...